The present invention relates generally to optical devices, such as sensor lens units for use in optical pickups of optical disk devices, and more particularly to an improved optical device which can reliably avoid an undesirable optical axis deviation resulting from thermal expansion or contraction of an optical body such as a lens.
Optical pickups employed in optical disk devices, such as CD, CD-R, CD-RW, CD-WO and DVD recording/reproduction devices, generally comprise various optical components including a laser diode, photodetector, half mirror and lens which are all incorporated within a predetermined frame. These optical components must be set in place accurately without any deviations of their optical axes and focal points.
For reduction in the costs and weights of the optical components, some of the conventional optical devices employ, in place of a traditional glass lens, a polycarbonate lens integrally formed with a mirror cylinder. FIGS. 7A and 7B are diagrams showing a typical manner in which such a lens integrally formed with a mirror cylinder is fixed within the frame. Namely, the integrated or one-piece structure 5 of the lens 3 and the mirror cylinder 4 surrounding and thereby protecting the lens 3 is inserted in a groove 2 that is formed in the die-cast frame 1 and defined by a slanted wall surface of the frame 1. In this way, the lens 3 is accurately positioned relative to the frame 1 and firmly secured to the frame 1 by means of an adhesive 6.
Further, it is generally necessary to guarantee an appropriate operating environment of the optical pickups in a wide temperature range. However, because the one-piece structure of the lens and the mirror cylinder is unremovably fixed directly to the frame by the adhesive, the conventionally-known optical devices encounter the problem that the center (optical axis) of the lens would undesirably deviate as the lens thermally expands or contracts, as shown in FIG. 7B. Particularly, because the polycarbonate lens has a very high thermal expansion coefficient as compared to the traditional glass lens, its optical axis deviation would exert non-negligible adverse influences upon a light detection unit of the disk recording/reproduction device.
In view of the foregoing, it is an object of the present invention to provide an improved optical device which can reliably avoid an optical axis deviation that would result from any possible thermal expansion or contraction of an optical component employed therein.
In order to accomplish the above-mentioned object, the present invention provides an optical device which comprises: a support having at least two supporting surfaces extending along at least two reference planes intersecting each other along a predetermined intersection line; an optical component including an optical body and at least two support arms extending outward from a periphery of the optical body, one of the support arms having one side surface abutting against one of the supporting surfaces, the other support arm having one side surface abutting against the other supporting surface, the optical component being supported by the support in such a manner that an optical axis of the optical body conforms with the intersecting line; securing means that presses the one side surface of each of the support arms against a corresponding one of the supporting surfaces, to thereby secure the optical component to the support in a half-fixed manner.
According to the present invention, the at least two support arms extending outward from the optical body are supported by the support in a half-fixed manner by being pressed against the corresponding supporting surfaces of the support. The at least two support arms of the optical component, as well as the corresponding supporting surfaces of the support, extend along at least two reference planes that intersect with each other at the optical axis of the optical component. Therefore, by the support arms of the optical component being pressed against the corresponding supporting surfaces, the optical axis of the optical component can be placed to positionally conform with the intersection line of the reference planes. Thus, as the optical component thermally expands or contracts, the support arms of the optical component, which are pressed against and half-fixed to the corresponding supporting surfaces of the support, are caused to move radially outward away from the optical axis along the supporting surfaces to thereby accommodate any dimensional deviation of the optical component due to the thermal expansion or contraction of the optical component. As a consequence, the present invention can reliably avoid an undesirable positional deviation of the optical axis.
In a preferred implementation of the present invention, the support includes three supporting surfaces and the optical component includes three support arms. Namely, assuming that first, second and third reference axes intersect at right angles with each other at a predetermined point and that a first reference plane is defined by the first and second reference axes and a second reference plane is defined by the second reference axis and third reference axis, the optical device of the present invention comprises: a support having first and second supporting surfaces extending along first and second reference planes extending along the first reference plane and a third supporting surface extending along the second reference plane, an optical component including an optical body and first, second and third support arms extending outward from a periphery of the optical body, the first support arm having one side surface abutting against the first supporting surface, the second support arm having one side surface abutting against the second supporting surface, the third support arm having one side surface abutting against the third supporting surface, the optical component being supported by the support in such a manner that the optical axis of the optical body conforms with the second reference axis; and securing means that presses the one side surfaces of the first, second and third support arms against the first, second and third supporting surfaces, respectively, to thereby secure the optical component to the support in a half-fixed manner.
In this invention, it is preferable that the distal and proximal ends of the first and second support arms be resiliently joined with each other, and that the distal ends of the first and second support arms be firmly secured to the first and second supporting surfaces, respectively while the proximal ends of the first and second support arms are secured to the first and second supporting surfaces, respectively, in a half-fixed manner.
If the positions of the distal ends of the first and second support arms which are secured to the first and second supporting surfaces deviate by a predetermined distance from optical-axial reference positions of the optical body, then the reference position of the optical component may deviate along the direction of the optical axis under the thermal influence. Thus, according to the present invention, the reference position of the optical component is intentionally set to deviate so as to accommodate any possible thermal influence on the optical component, with the result that thermal characteristics of the inventive optical device can be improved even further.